Obesity: the role of fatty foods.

Obesity: The role of fatty foods

Scientists continue to puzzle over why some people plump out and others remain thin. Clearly diet plays a role, but that role "may be more complicated than originally assumed," say researchers at Indiana University in Bloomington. Their latest work suggests it's the relative proportion of fat in the diet -- far more than total calories consumed -- that fosters obesity.

Wayne C. Miller and his co-workers surveyed diets and exercise among 107 men and 109 women. After instructing their volunteers on how to estimate dietary portions, the scientists asked them to recall food consumed over the past day, log consumption over another two days, and describe dietary preferences. In the September AMERICAN JOURNAL OF CLINICAL NUTRITION, Millerhs team reports that "the only distinct difference" in eating behavior between lean and obese adults was the source of their calories. Lean men and women got about 29 percent of their calories from fat and 53 percent from carbohydrates. Obese subjects, by contrast, derived 35 percent of their energy from fat and only 46 percent from carbohydrates.

Per pound of body weight, fatter individuals ate fewer calories, the researchers found. And though svelter subjects exercised much more, Miller suspects this alone does not account for the major difference in body weights, and points to a pair of studies his team conducted in 1984 and '87. In those studies, rats receiving 40 percent of their calories from fat put on twice as much body fat as animals consuming the same calories -- or even more -- but receiving just 11 percent of their energy from fat. His new study now appears to extend this trend to humans: Among thos eating the same number of calories, the more rotund proved to be those who routinely eat more fat.